The Petard was an Kuan Ti-class DropShip owned and operated until at least 3067 by the mercenary unit known as The Medusans. The Petard was serving as the CCSS Shen Zhen, a Capellan Confederation ship under the command of the Death Commandos when the Commandos launched an attack on an aid convoy above Targa during the Capellan-St. Ives War. Unfortunately for the Death Commando strike team, Hydra Squadron was deployed in the area at the time and swapped positions with the convoy craft, who grounded on the surface of Targa; this left the Commandos facing a complete assault squadron. The Commandos lost two companies in the resulting battle, along with the Shen Zhen, which was captured by Hydra Squadron and renamed the Petard.[1]

Petard remained in service with the mercenaries, replacing a Leopard CV which had been destroyed during the same battle, and the Petard and the Achilles-class Achilles II formed the Third Division of Hydra Assault Squadron in 3067, serving under the commanding officer of the Third Division, CaptainJonathan "Hooky" Bell.[1]

When the Medusans attempted to defend New Syrtis from a Capellan strike force in 3069, the Petard was one of the ships involved in launching a deep space ambush against the Capellans. While the Medusans managed to destroy a Leopard and a Triumph and damaged a number of other Capellan DropShips, the mercenaries took damage in turn from the Capellan forces led by the Impavido class WarShipCCS Zhejiang, which was escorting the strike force. Petard took damage during the combat, and while the damage was repairable, the damage inflicted on shipyards throughout the Inner Sphere by the Word of Blake as the Jihad escalated meant that the Petard was still waiting for those repairs at the end of 3071.[2]